ActionController::Metal by default provides no utilities for
rendering views, partials, or other responses aside from explicitly calling
of response_body=, content_type=, and
status=. To add the render helpers you're used to having
in a normal controller, you can do the following:

Returns the last part of the controller's name, underscored, without
the ending Controller. For instance, PostsController returns
posts. Namespaces are left out, so Admin::PostsController
returns posts as well.